Variable-speed dynamo.



PATENTED DEG. 13, l904.

A. J. EARNSWORTH.

VARIABLE SPEED DYNAMO.

APPLICATION FILED AUG. 1, 1902.

No MODEL. 2 SHEETS-SHEET 1.

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VAK/ABLE F/EL CONSTANT F/EL VAR/AELE FIELD CONSTANT FIELD l WTFAEEJEEE:

PATENTBD DEG. 1s, 1904.

A. J. EARNSWOETH. VARIABLE SPEED DYNAMO.

APPLICATION FILED AUG.1, 1902.

2 SHEETS-SHEET 2A N() MODEL.

SPEED WTHEEEEE:

MM C@ M UNITED STATES Patented Decembei` 13, 1904.

PATENT OEEICE.

ARTHUR J. FARNSWORTH, OF NEW YORI, N. Y., ASSIGN OR TO RAILIVAY ELECTRICAL IMPROVEMENT COMPANY, OF NEW YORK, N. Y., A COR- PORATION OF NEW JERSEY.

VARIABLE-SPEED DYNANIO.

SPECIFICATION forming part of Letters Patent No. 777,194, daued December 13, 1904.

Appiication led August 1, 1902.

To LZZ 'wwnt 'it Netty concern:

Be it known that I, ARTHUR J. FARNswoE'rH,

a citizen of the United States, residing in the boroug'h of Manhattan, city, county, and State of New York, have invented an Improvement in Variable-Speed Dynamos, of which the following description, in connection with the accompanying drawings, is a specification, like letters on the drawings representing like parts.

My invention consists in a system of electrical distribution, being concerned more particularly with a combination of d ynaino-electric elements applied in the illustrative embodiment herein to the generation of a substantially constant potential through driving means subject to an irregular or variable speed, the invention being particularly useful where the speed of the driving' means varies over a wide range.

One method of maintaining a constant p0- tential at the terminals of a variable-speed dynamo is by varying the field strength inversely with the speed, the same being weaky ened orstrengthened, respectively, on increase 2 5 or decrease in speed. It has been attempted to carry out this method by opposing the effect of the main exciting-coil of the generator by the effect of one or more coils, the current in which is made to increase on rise of speed. Regulation based upon this principle, however, has failed to more than roughly approximate the required potential, owing to the failure of the ield strength to follow the necessary law of variation. I have so arranged and constructed my improved dynamo that a substantially constant potential can be maintained at all rates of speed between the limits for which the machine is designed.

My invention will be best understood from 40 the accompanying description and illust-ration of several specific embodiments thereof, it being understood that it is in no sense limited to the particular form and arrangement of parts herein disclosed, while its scope will be more fully pointed out in the appended claims.

Referring to the drawings, Figure 1 shows in a diagrammatic view a variable-speed d v- Serial No. 118,026. (No model.)

namo constructed according to my invention. Figs. 2, 3, and 4 show various modifications in diagram of my broad idea. Fig. 5 shows 50 in a diagrammatical development the relation between the arinature-windings and fields in the dynamo shown in Fig. 1, and Fig. 6 shows an explanatory curve.

Referring' to Fig. 1, A is the armature of a 55 d ynamo-electric machine, comprising thc two adjacent portions (t and d, preferably of different diameter, to which rotation may be imparted in any desired manner from any suitable source of power, which in the present in- 6o stance is supposed to be subject to wide variations in speed. The field-magnet of this machine may be of any appropriate construction, but preferably comprises two independent magnetic circuits, which I have herein conventionally represented by the two lield-magnets and the former adapted to produce a variable and the latter a substantially constant iield of force. Field-magnet which maintains the constant iield, is provided with 7o a winding' c, preferably connected to a source of constant clectromotive force, such as a storage battery B, and including' in series the adjusting-rheostat R. Field-magnet b, which creates the variable lield, is provided with the winding' c, connected through the brushes e and commutatorf to the auxiliary armaturewinding g/, Fig. 5, carried by the larger portion a of the armature and preferably adapted to revolve only within the constant lield of 8o force produced by magnet so as to maintain a current varying substantially with the speed of the armature. A rheostat R affords means for varying' the resistance of the circuit, including the winding c. The armature 8 5 A also has a main winding 0, Eig. 5, extending substantially the entire length of thc two portions a and c of the same, so arranged as to cut the lines of force created by both the constant and the variable lield and to produce 9o thereby an electromotive force which is the resultant or algebraic sum of the electromotive forces produced by the effect of the two magnetic lields upon winding y. finding g is connected to commutator f and supplies current through brushes e to any desired consumption-circuit, as C.

To illustrate more clearly the relations or' the lields to the armature-windings and the armature-windings to each other, I have shown in Fig. 5 the development of' a machine having two distinct magnetic circuits of' four poles each and provided with a wave-winding for the armature, all arranged according to the abovedescribed embodiment of my invention. It will ot' course be understood that the specific arrangement or number of poles and the character of the windings is immaterial, and this is merely selected to illustrate one special application of my broad idea. Referring to Fig. 5, N S N S represent the four poles of field-magnet b, excited by winding c, Fig. l, and producing' the variable field. N' S N S represent the poles of field-magnet excited by the constant-current winding c', producing the constant field. Armature-winding r ,shown connected to commutatorf, is adapted to cut the lines of force from both sets of poles,

while armature-winding g' is in operative relations to poles i Sl N/ S/ only.

The manner in which regulation is effected will be apparentfrom the following considerations: Since the eleetromotive i'orce in any given machine is afunction only of the speed and the lield strength to maintain it at a constant value, the field strength should vary inversely with the speed. Fig. 6 shows a curve plotted with speeds as abscissae and field strengths as ordinates following the equation FS:a constant, where F represents field strength and S the speed, illustrating the law of variation of' field strength necessary to produce a constant eleetromotive force. This, it will be seen, is curvilinear and closely resembles in form an inversion of the well-known magnetization or saturation curves of various magnetic mediumsthat is to say, at low speeds comparatively great changes in field strength are necessary to correct for slight variations in speed, while at high speeds corresponding variations in speed require comparatively slight changes in iield strength, precisely as great changes in the magnetization of iron or other magnetic material are produced by small variations in the excitingcurrent when the iron is removed from the condition ot' saturation, while comparatively slight changes are effected by corresponding variations in the exciting-current when the condition ot' saturation is approached. Theretore if the actual effective field of torce in which the armature-conductors are rotated is varied inversely with the speed according to the same law that the curve ot' magnetization follows, the eleetromotive torce produced will be substantially constant within the limits oi' speed between which the magnetization curve closely resembles theV curve shown in Fig. G. ln the embodiment of my invention shown in Figs. land 5 I have so arranged the connections that the effect or' the main or constant iield produced by winding d upon the main winding g is opposed by the etlect ot the variable field produced by winding c. The current strength in the latter winding being' directly proportional to the speed of the armature, the field created thereby varies with the speed of the armature, but according to the curve of' magnetization of the magnetic medium of which its magnet-core is composed. The opposition ot' the eleetromotive torce generated in the main armature-winding r/ by the variable field to the eleetromotive torce generated by the constant lield produces at any given speed a resultant eleetromotive torcel which is a function of the speed and the actual effective field strength, the latter being equal to the strength ot' the constant lield, assumed to be the greater, less that ot the variable field. This eflective lield strength is equal to a constant quantity less a quantity varying along the magnetization curve of the material used, and therefore by the selection ot' proper proportions in a manner well known to those skilled in the art may be made to tollow within certain predetermined limits a law of variations substantially the same as shown in the theoretical curve of Fig. 6.

To obtain the best regulation, it is preterable to so proportion the different parts oli the machine that the exciting-currents f'or winding c, corresponding to the speed limits between which it is desired to obtain a constantpotential regulation, may be such as to cause the limits of' magnetization of held-magnet 7 to embrace between them that part ofl the saturation or magnetization curve most nearly coinciding' with the theoretically -required curve, and it is also desirable to select tor the magnet 7) that material having a magnetization curve coinciding to the greatest extent with the theoretical curve; but it will be imderstood that my invention is not limited to any particular kind ot magnetic material for held-magnet or to such arrangement ot parts as necessitates working said held-magnet along any particular part ot' said curve.

In Fig. 2 I have illustrated another embodiment of' my invention wherein the two dynainos A and A/ have their armatures t and /z/ mounted upon the saine shaft, but provided with independent windings. As in the 't'oregoing instance, armature a revolves within a field maintained by a current Vfrom a source ot constant potential and generates an electromotive force varying with the speed. rinding c on magnet is connected in shunt across the terminals ot' machine A and accordingly receives an exciting-ciirrent varying with the speed ot' the armatures. The armature-windings of the two machines are connected in series, so that the eleetromotive force generated in 0/ is opposed by the lesser counter eleetromotive torce generated in a, and since the rc- IOO IIO

sultant electromotive force of the consumption-circuit C depends upon the actual effective magnetization of the two machines by the selection of' proper proportions between the diierent elements well understood by those familiar with the art a substantially constant potential may be impressed upon the consumption-circuit C within certain predetermined limits of speed. I/Vhile I have here shown the two armatures mounted upon the same shaft, it is evident that they may be so mounted forming parts either of a single unitary machine or of otherwise independent machines, or the two machines and their armatures may be mechanically separate and distinct, all these and many other modifications being comprehended within the scope of my invention.

In Figs. 3 and i I have shown arrangements of connections similar to those already described in connection with Figs. l and 2, respectively, whereby the battery B, employed to excite the constant field, is dispensed with, the winding c being directly connected in shunt to the constant-potential consumptioncircuit C. In other respects the connections are similar to those already disclosed, andthe mode of operation will be readily understood from the foregoing description.

The proportions of the various parts necessary to obtain the proper relations between the two magnetic fields and other quantities will be readily understood by those familiar with the art, to whom also will occur many other specific arrangements of parts and modifications of my broad idea which I have deemed unnecessary to illustrate herein, but which, together with those I have submitted for illustrative purposes, are comprehended within the scope of my invention.

I claiml. A variable-speed-generating device having a magnetic field the strength of which is substantially independent of the speed variations, a generating-circuit relatively movable at a'variable speed within said field, and means for producing a corrective electromotive force in said circuit comprising a magnetic field, the strength of which varies with the relative movement of' said generating circuit at a greater rate at low speeds than at high speeds and within which field said generating-circuit is also relatively movable.

2. A variable-speeel-generating device having a magnetic field the strength of which is substantially independent of the speed variations, a g'enerating-circuit relatively movable at a variable speed within said field, and means for producing a corrective electromotive force comprising a variable field the strength of which varies with the relative movement of' said generating-circuit along the curve ofl mag'- netization of the material ofl its magnet-core, said generating-circuit being also relatively movable within said variable field.

3. A variable-speed dynamo-electric device having a field substantially independent of speed variations, au armature relatively7 movable at a variable speed within said field, and means for impressing upon the armaturecircuit a corrective electromotive force, said means comprising a variable field varying with the relative armature movement within said first field, said two fields having different magnetic circuits.

4L. A variable-speed dynamo-electric device having a main field, an armature relatively movable at a variable speed within said field, and means for impressing upon the armaturecircuit a corrective electromotive force, said means comprising a variable field having a dierent magnetic circuit from said main field and having a streng'th varying with the relative armature movement within said main field.

5. A variable-speed dynamo-electric machine having' a field the strength of which is substantially independent of the speed variations, an armature relatively movable therein, and means for impressing upon a different portion of the armature-circuit a corrective electromotive force, said means comprising a variable field varying with the relative armature movement within said first field, and connecting means between the two portions ofl said armature-circuit to cause proportionate movement thereof relatively to their respective fields.

6. A variable-speed constant-potential generating device comprising a field-magnet excited from the constant-potential terminals thereof, an armature relatively movable within the field created by said magnet, a second field-magnet excited by energy derived from the rotation of said armature within the field of said first magnet and means for impressing upon the generating-circuit of' said device by means of said second field-magnet a corrective electromotive force varying with the speed.

7. In a constant-potential variable-speed dynamo-electric machine a field-magnet having` an excitation substantially independent of speed variation, a second field-magnet having an excitation varying' with the dynamo speed and series-connected conductors adapted to have variable movement relatively to each field, said fields being so related as to produce opposing eufects in said conductors.

8. In a constant-potential variable-speed dynamo-electric machine, a field-magnet having an excitation independent of speed variations, a second field-magnet having an excitation varying with the speed ofl said machine along the magnetization curve and series-connected conductors adapted to have movement relatively to each field, said fields being so related as to produce opposing' effects in said conductors.

9. A variable-speed dynamo having a fieldmagnet with an excitation substantially inde- IOO pendent of speed variations, -a second fieldmagnet excited by an auxiliary armaturewinding rotat-able within the field of' said first niagnet, and a main armature-winding rotatable within both fields, said fields being so related as to produce opposing electromotive forces in the said main armature-winding.

10. A variable-speed constant-potential dynamo having a field-magnet provided with exciting-coils connected to the constant-potential terminals ofl said dynamo, a second fieldmagnet excited by an auxiliary armaturewinding' rotatable within the field created by said first magnet and a main armature-winding rotatable within both fields, said fields being so related as to produce opposing electromotive forces and a substantially constant resultant electromotive force in said main armature-winding.

11. In a variable-speed constant-potential generating device, a generating-circuit, magnetizing means therefor, and means for causing the actual effective field magnetization to vary inversely with the speed substantially according to the curve of saturation of' the material of which the field magnet or magnets is composed, the rate of' variation being' greater at low speeds than at high speeds.

12. In a variable-speed constant-potential generating system the combination of a generating-circuit, magnetizing' means therefor and means f'or causing the actual effective field magnetization to vary suitably to produce a constant electromotive force by means of a component substantially independent of' the speed opposed b v a component varying with the speed along' the curve of' magnetization of the material of which the field magnet or magnets is composed.

13. A variable-speed dynamo having a generating-circuit adapted to cut at a variable speed the lines of force from two magnetic fields, one of which is derived from a magnetic circuit having an excitation substantially independent of speed variations and the other from a different magnetic circuit having exciting-current varying substantially in proportion to the speed.

14. A variable-speed dynamo-electric machine having a main field-magnet excitation the strength ofl which is substantially independent of' speed variations, a second fieldmagnet having avariable excitation, an armature relatively movable within the fields created by both said magnets and an armaturewinding for exciting' said second field-magnet, said armature being relatively movable within said main field only.

15. A variable-speed constant-potential dynamo-electric machine having a resultant effective field magnetization one component of which varies with the speed according to the curve of magnetization ofl the field-mag'- net material, with adiminishing rate of' variation at the higher speeds.

16. A variable-speed constant-potential dynamo-electric machine having' a resultant effective field magnetization one component of which varies with the speed of the dynamoelectric machine according to the curve ofI magnetization of the field-magnet material and the other component ofI which remains substantially constant irrespective of the dynamo speed.

17. A constant-potential variable-speedgenerating system comprising' means for impressing upon the consumption-circuit thereof two electromotive forces, one of which is generated bythe relative movement at a variable speed of a generating conductor or conductoi's within a field substantially independent of the speed variations of said conductors and the other ofI which is produced by the relative movement of a generating conductor or conductors within a variable field, the strength of` which varies with the movement of' said conductors within said first field.

18. Aconstant-potential generating system comprisingl means for impressing upon the consumption-circuit thereofl two electromotive forces, one of which is produced by the relative movement of' generating-conductors at a varying' speed within a main field and the other by a similarly vai'yingmovement of generating-conductors relatively to and within a variable field, said variable field varying with the speed of said conductor or conductors according to the curve of' magnetization of' its field-magnet material.

19. A dynamo-electric machine having an armature\vin :ling, two independent magnetic fields within which said armature-winding is relatively movable, means f'or providing one of said fields with excitation substantially independent of variations in the ai'mature speed of` said machine, and means for providing the other of said fields with an excitation varying' substantially in direct proportion to the armature speed.

20. A variable-speed eonstant-potential dyaname having' a main armaturewinding operatively related to two magnetic elements and an arinature-winding for exciting one of said. elements rotatable within the field created by the other.

21. A dynamo-electric machine having a portion of` its armature.-winding' affected only by a magnetic field, the strength of which is substantially independent of speed variations, and a second portion of its armature-winding, which is electrically connected with the first in an opposed direction, affected only by a magnetic field, the exciting-current of which is substantially proportional to the armature speed.

22. A dynamo-electric machine having a magnetic field excited by a current, the strength of which is substantially independent of speed variations, and provided also with a second magnetic field excited by a current, the

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strength of which is substantially propor- In testimony whereof I have signed my naine tlonal to the armature speed, and an arnmtureto this specification 1n the presence of two sul Winding, a portion ot which revolves 1n and Scribing Witnesses.

is affected only by the rst field, and a Second ARTHUR J. FARNSVVORTH. 5 portion of which, electrically connected with VtneSSeS:

the rst in an opposed direction, revolves in N. G. JOHNSON, and is affected only by the second field. l

J. L. WATSON. 

